JNTU
JNTU B.Tech II ELECTRICAL TECHNOLOGY Previous Question Paper (August/September - 2022 - R16)
Answer any five questions
All questions carry equal marks
Main
Derive the torque equation of a DC motor.
Answer
The mechanical power developed in a DC motor is the product of the electromagnetic torque (Ta) and the angular velocity (ω). From the electrical power equation, the power developed is P = EbIa, where Eb is the back EMF and Ia is the armature current.
The back EMF equation is given by:
Equating electrical power to mechanical power (Ta × ω):
Solving for Ta:
Where φ is flux per pole, Z is the total number of armature conductors, P is the number of poles, Ia is the armature current, and A is the number of parallel paths.
A 6-pole wave connected DC generator having 60 slots on its armature with 6 conductors per slot, runs at 750 rpm and generates an open circuit voltage of 230 V. Find the useful flux per pole.
Answer
Given parameters: P = 6, A = 2 (for wave connection), Z = 60 slots × 6 conductors/slot = 360 conductors, N = 750 rpm, Eg = 230 V.
The EMF equation for a DC generator is:
Substituting the values:
Calculating the flux per pole:
The useful flux per pole is approximately 8.52 mWb.
Explain in detail about the classification of DC generators.
Answer
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A 200V DC shunt motor takes a total current of 100A and runs at 750 rpm. The resistance of the armature winding and shunt field winding is 0.1 ohms and 40 ohms respectively. Find the total copper losses.
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Derive the induced e.m.f equation of transformer.
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A 15kVA, 1-phase, 50Hz, 500/250V transformer gave following test results: OC test (LV) side: 250V, 4.0A, 200W; SC test (HV) side: 25V, 30A, 300W. Calculate efficiency and regulation at full-load, 0.9 p.f lagging.
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Describe the construction details of a 1-φ transformer?
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Draw the phasor diagram of 1-φ transformer on no-load.
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Draw and explain the Torque-Slip characteristics of a 3-phase Induction Motor.
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The frequency of emf in the stator of a 4-pole induction motor is 50Hz, and that of rotor is 1.5Hz. Calculate slip and at what speed will the motor run?
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Compare slip ring and squirrel cage induction motors.
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Explain any one of the starting methods of 3-phase Induction motor.
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What is distribution and coil span factors? Explain.
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Explain the principle of operation of Alternator.
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Explain the working principle of a shaded pole motor.
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Write short notes on Attraction type of Moving iron instrument.
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